Yarn heater

ABSTRACT

A yarn heater having substantially equidimensional, coiled lengths of electrical resistance wire interconnected by a coilreversing loop is located coaxially of a running yarn and does not require a free end of yarn for stringup.

United States Patent [191 David 1 May8,1973

Z YARN HEATER [75] Inventor: Israel A. David, Wilmington, Del.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

[22] Filed: June 22, 1971 [21] Appl. No.: 155,465

[52] U.S. Cl ..219/388, 28/62, 57/34 HS, 219/521, 219/553, 338/62 [51] Int. Cl ..F27b 9/06 [58] Field of Search ..219/388, 521, 530, 219/540, 552-553; 28/62; 338/6063, 64; 174/33, 34; 57/34 HS [5 6] References Cited UNITED STATES PATENTS 2,864,931 12/1958 Stoddard et a1. ..219/388 2,869,312 1/1959 Van Dijk 2,931,000 3/1960 Gordon et al. ..338/62 1,347,900 7/1920 Englund ..388/61 2,831,639 6/1958 Planer et a1. ..338/62 2,891,227 6/1959 Boykin ..338/62 FOREIGN PATENTS OR APPLICATIONS 513,216 10/1920 France ..219/553 729,780 3/1966 Canada 599,394 6/1934 Germany.... 643,123 3/1937 Germany 253,165 6/1926 Great Britain ..338/63 Primary Examiner-Velodymyr Y. Mayewsky Attorney-J. R: McGrath [57] ABSTRACT A yarn heater having substantially equidimensional, coiled lengths of electrical resistance wire interconnected by a coil-reversing loop is located coaxially of a running yarn and does not require a free end of yarn for stringup.

2 Claims, 5 Drawing Figures PA'IENTEDMY' 81w 3,732,395

SHEET 2 OF 2 FIG-4 YARN HEATER 7 BACKGROUND OF THE INVENTION This invention relates to an improved heater for heating running yarns and, more particularly, to a coiled wire heater which can be strung up without having a free end of yarn and without moving or demounting the previously aligned heater.

Devices for heating running yarns are numerous and well known. These include hot chests, heated rolls, heated pins, hot plates, heated tubular passageways and jets of hot gas, to name a few. It is also known to use a resilient coil of electrically heated wire for heat setting. Particularly in the texturing of yarns by false twisting has the need developed for efficient, high speed, small heaters for heat setting the twisted yarns. None of the known heaters is completely satisfactory in that: they heat the yarn along only one contacting side so as to require long times and large sizes for raising yarns uniformly to their heat setting temperatures; they require a free end of yarn for stringup which therefore becomes difficult or impossible when high temperatures are involved; they are inefficient in terms of the fraction of their energy consumption actually used to accomplish heat setting; or their heat capacities are so great that they cannot be quickly heated to operating temperatures or cooled down for easy handling.

SUMMARY OF THE INVENTION The disadvantages listed above have been overcome in a small, easily and inexpensively fabricated apparatus for heating a running yarn. The heater has two coiled lengths of electrical resistance wire interconnected by a coil-reversing loop and is located coaxially with the path of advance for yarn running between spaced supports in a yarn-handling installation. The coiled lengths have the same number of coils of the same dimensions. The inner diameters of the coils provide a passage at least as large as the effective diameter of the yarn and adjacent coils are also spaced sufficiently to allow for entry of the yarn during stringup.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents schematically a preferred yarn heater of the invention.

FIG. 2 is an alternative form of the yarn heater of the invention.

FIG. 3 is a modification of the yarn heater of FIG. 2.

FIG. 4 is a perspective view of a false twisting process and apparatus utilizing the yarn heater of FIG. 1.

FIG. 5 is a sectional view through the type of resistance wire shown schematically in FIGS. 1-4.

DESCRIPTION OF THE INVENTION Yarn heater of FIG. 1 represents a generally preferred embodiment of this invention. It is constructed of an electrical resistance heating wire doubled back at approximately its center to form a coilreversing loop 12. For clarity, lengths l4, l6 and the reversing loop are represented as lines. Ordinarily, however, these wires have an appreciable diameter as compared to the free space between adjacent coils. An enlarged cross section is shown in FIG. 5. Lengths l4, 16 are twisted together back from reversing loop 12 in the form of a double stranded helix of one hand and have the same number of helical coils about supported yarn path 18. The inner diameter of these helices must at least slightly exceed the effective diameter of yarn to be treated but it can be as much larger as desired for obtaining a preselected heating effect. The spacing between adjacent coils must everwhere be at least large enough to allow for stringup of the yarn. The ends of coiled lengths 14, 16 remote from reversing loop 12 are bent away from yarn path 18 and each is adapted for attachment to one pole of a supply of electrical energy. As shown in FIG. 1, the two ends are rigidly held, in known fashion, in a suitable electrical plug 20 which provides for both electrical energization and physical support when yarn heater 10 is plugged into a corresponding electrical receptacle (not shown). In this embodiment, lengths 14, 16 are helically coiled around the same portion of yarn path 18, about out of phase, in the same helical sense. A yarn (not shown) passing generally parallel to the yarn path but outside the heater is readily strung up by plucking the yarn beyond reversing loop 12 and rotating it counterclockwise about the helices of heater 10 so that it winds between the coils from left to right as shown. The number of times yarn must be rotated about device 10 equals the number of coils in each wire portion.

In the yarn heater 10 shown in FIG. 2, coiled lengths 14', 16', however, are seen to be coiled about successive portions of supported yarn path 18'. In this case, where the helices of lengths 14, 16' are not intercoiled, both the coiling direction and helical sense or hand of coiling invert as one traces advance of the coils through reversing loop 12'. Thus, the resistance wire is in the form of an inverted helix, the hand of which changes at loop 12'. In this device, stringup is accomplished by plucking a stationary or running yarn near the reversing loop and rotating the plucked point outside of the coils so that the yarn is fed first between the coils remote from the reversing loop and progressively closer to it until completely coincident with yarn path 18. Here again, the coiled lengths are adapted for installation coaxially of the yarn path and include the same number of coils of substantially the same dimensions.

The alternative device 10" of FIG. 3 is similar to that of FIG. 2 except that reversing loop 12" is bent so that supported yarn path 18" changes direction at idler roll 22. A section of low resistance electrical lead 24 interconnects coiled lengths 14", 16" in reversing loop 12". Leads 26" represent electrical connections to a source (not shown) of electrical power.

Yarn heaters of this invention are particularly suited to heat setting running yarns during false twisting. FIG. 4 illustrates a false twist installation using yarn heater 10. The apparatus shown is basically a draw twister of which only the upper rail 28 of the 'frame is shown. Well known draw winders, up-twisters and downtwisters can be similarly modified to produce torque stretch yarns by false twisting. In FIG. 4, undrawn yarn 30 is withdrawn from a supply thereof (not shown) through guide 32 and through the nip between cot roll 34 and driven feed roll 36. By passing around draw pin 38 and in several wraps around draw roll 40 and separator roll 42, yarn 30 is drawn. Drawn yarn 30 passes linearly .from the nip of draw roll 40 and spring loaded roll 44 up to guide 46, i.e., rolls 40, 44 and guide 46 function as supports and define a supported yarn path. In this linear false twisting zone, yarn 30 undergoes heat setting in yarn heater 10. Pneumatic torque jet 48 simultaneously twists and cools yarn 30. Yarn cleaner 50 (or a similar barrier) may be employed to protect yarn heater from the cold exhaust gases from torque jet 48. From guide 46, yarn 30 travels over snubbing pins 52, in several wraps around the smaller, relaxing step 41 of roll 40 and its associated step 43 of separator roll 42, and through guide 54 to package 56. In a draw-twister, as shown, a small amount of real twist is introduced by the over end, ring-and-traveler packaging. A draw winder differs essentially in that the yarn is wound by a traversing mechanism which introduces no additional twist.

In utilizing yarn heater 10 in FIG. 4, the whole process can be strung up with yarn 30 passing outside heater 10. Then, as previously described, yarn 30 is brought to pass along the helical axis of heater 10 simply by plucking it and winding it about the coils. Electrical energization of heater 10 is easily accomplished when its plug is an electrical receptacle 60 which has previously been rigidly located to hold heater 10 in the desired position relative to the supported yarn path. Electrical leads to receptacle 60 come from a variable source of regulated electrical power (not shown). By using an inner coil diameter of heater 10 only slightly larger than the effective diameter of yarn 30, yarn vibrations set up by torque jet 48 cause yarn 30 to contact all inner surfaces of heater 10 whereby uniform heating is assured.

Suitable electrical resistance heating wire for use in the heaters of this invention should be able to generate and withstand temperatures of about 700 C. or higher. A number of alloys are well known for these characteristics, the best known of which is Nichrome" wire (Nichrome is a registered trademark of the Driver- I-Iarris Co.). While not limited thereto, the diameter of such wire is ordinarily in the range of 18 to 40 mils (0.457 to 1.02 mm.). Further preferred, but not limiting, areas of operation include an inner coil diameter of 3 to 10 mils (0.076 to 0.254 mm.), a coil pitch of 0.1 to 0.3 inch (0.25 to 0.76 cm.), a wire temperature of 800 to l,200 C., and a length of yarn path in the heating device selected to provide a residence time of less than 0.050 sec. (usually 0.003 to 0.012 sec.). By exposing a running yarn to such high temperatures for extremely short times, very effective heat setting is achieved without any melting of the yarn. The wire coil heaters of this invention are very much smaller than heretofore known yarn heaters and can be incorporated in virtually any yarn-handling installation without modifications to provide extra space. Typical wire coil heaters consume less than 100 watts of electrical energy. They have the further advantages that they reach elevated operating temperatures almost immediately after ener gization, that they cool off very rapidly when current is turned off, and that their temperature is readily regulated by maintaining a constant supply current.

EXAMPLEI A three-filament undrawn polyhexamethylene adipamide yarn is false twisted substantially as shown in FIG. 4 except for utilizing traversing windup rather than an over-the-end windup. As drawn and fed to heater 10,

its denier is about 21. Heater 10 is 1 inch (2.54 cm.) long is constructed of 28.5 mil (0.724 mm.) diameter Nichrome wire, has 5.5 coils in the helix of each of lengths 14, 16, has an inner coil diameter of 10 mils (0.254 mm.), carries a current of 14 amperesand maintains a coil temperature of 970 C. during processing. Feed roll 36 and draw roll 40 are driven differentially to provide a draw ratio of 4.1X. Yarn speed on draw roll 40 is 593 ydJmin. (542 m./min.) and on relaxing step 41 is 17.5 percent less. Yarn 30 undergoes an additional 2.8 percent relaxation between relaxing step 41 and the traversing windup. From the nip of roll 44 to the entrance of yarn heater 10 is 5.5 inches 14.0 cm.). From the exit of yarn heater 10 to the entrance of the 15 mil. (0.38 mm.) diameter yarn passage of torque jet 48 is 5.19 inches (13.18 cm.). The resultant yarn has a twist of turns per inch (23.6 turns/cm.) and 76 crimps per inch (29.9 crimps/cm.).

Twist is determined by doubling a length of untwisted yarn from the package, hanging a weight of 1.2 mg./den. from the loop and then releasing the two lengths to twist around one another while exposing the bundle to saturated steam at C. The twisted bundle is mounted in a conventional twist counter under constant tension of 10 grams. Initial length of the twisted bundle is noted; then, the number of turns required to return the two lengths to parallelism is measured. This number, divided by the initial twisted length, is reported as twist.

Crimp is obtained by first steaming a single filament of the yarn under 1.2 mg./den. tension. It is reported as v the number of cyclic deformations counted per unit length of the completely relaxed filament.

A companion test is run replacing yarn heater 10 with a hot air jet. All conditions are as nearly as possible identical to the above. Best operation requires reducing relaxation between draw roll 40 and relaxing step 41 to 15 percent. The larger heater also necessitates considerable lengthening of the supported yarn path between nip roll 44 and yarn guide 46. The heater is essentially a 7-inch (17.8 cm.) long tube through which hot air is jetted concurrently with the yarn, the supply air being at about 300 C. and the exit air about C. The resultant false twisted yarn has a twist of only 44 turns/inch (17.3 turns/cm.).

EXAMPLE II constant length through a yarn heater as shown in FIG.

2. The heater is constructed of 19 mil (0.48 mm.) Nichrome wire, is about 0.75 inch (1.90 cm.) long, has two coils in each wire portion, and provides an inner coil diameter of about 2 mils (0.05 mm.). It carries 5 amperes of electrical current. The heat treated yarn is packaged at a 4 percent underwind. Ladies sheer hosiery knitted from this yarn have a subjective shininess rating of 3.5 on a scale of 1 to 5 from most to least shiny. Hose knitted from the unheated control have a shininess of 1. Shrinkage of the heated yarn caused by immersion in boiling water is 6.1 percent as compared to 1 1.8 percent for the control.

EXAMPLE 111 A 2l-denier 3-filament polyhexamethylene adipamide yarn is textured on a modified draw twister of the type shown in FIG. 4. Over-the-end ring-and-traveler windup is employed with the yarn maintained at substantially constant length between relaxing step 41 and package 56. Processing conditions for this example and for two comparisons run by replacing heater with a hot air jet are shown in Table 1. Table 2 shows properties of resultant yarns.

TABLE 1 Yarn Heater Example Hot air Hot air Ill Jet Jet Draw-roll speed, ydJmin. 598 500 398 (m./min.) (547) (457) (364) Draw ratio 4.106X 4.106X 4.106X Relaxation (Roll l2) l6 l6 l8 Torque Jet Inlet Air Pressure, psig. 150 150 90 (kg/cm!) (10.55) (10.55) (6.33) Hot air jet Inlet pressure, psig. l8 l3 (kg/cm!) (1.26) (0.91) Supply air temp., C. 300 290 Wattage 137 l 16 Wire Coil Heater Wire diameter mils 28.5 (mm.) (0.724) Length, in. 2.0 (cm.) (5 .08) Inside diameter, mils 5.0

(mm.) (0.127) Coils per wire portion 12 Wire temperature, C. 865 Wattage 55 TABLE 2 Yarn Heater Example Hot alr Hot air [11 Jet Jet Draw roll speed, yd./min. 598 500 398 (m./min.) (547) (457) (364) Twist, turns/in. 61.9 55.0 54.2 (tums/cm.) (24.4) (21.7) (21.3) Crimp, crimps/in. 2 68 =57 (crimps/cm.) (32.3) (26.8) =(22) Hose area after boiling, in. 20.3 27.6 27.9 (cm' (131) (178) (180) Boarded hose length, in. 14.6 14.2 14.3 (cm.) (37.1) 36.1) (36.3) Hose power, gm. 640 450 460 It is seen that the coiled heater is much more economical of electric power and permits operating at yarn speeds of more than 100 yd./min. (91 m./min.) faster while producing yarns with more twist and more crimp. Moreover, hose knitted in identical fashion and then boiled in water have reduced area and higher power. Hose power is the force in grams required to extend a hose to a cm. length. Still further, stringup of the hot air jets requires a free end of yarn and is accomplished only with great difficulty since melting easily occurs at the temperatures used. Stringup of the wire coil, however, is accomplished with the yarn running and heater 10 too cool to cause melting. Operating temperature is achieved almost instantaneously thereafter by increasing electrical current supplied.

Instead of the solid, round, resistance wire shown in FIG. 5, other configurations, e.g., rectangular, either solid or hollow, could also be used. These and other variations of a similar nature will occur to those skilled in the art without departing from the scope of the invention which is accordingly intended to be limited onlly by the scope of the a pended claims.

avmg thus described he invention, what is claimed as new and desired to be secured by Letters Patent is:

1. In a yarn-handling installation including spaced supports defining a path of advance for running yarn, a heater comprising two coiled lengths of electrical resistance wire interconnected by a coil-reversing loop, said coiled lengths being substantially coaxial with said path and including the same number of spaced coils of substantially the same coil pitch and diameter, said coiled lengths being in the form of a double stranded helix of the same hand.

2. In a yarn-handling installation including spaced supports defining a path of advance for running yarn, a heater comprising two coiled lengths of electrical resistance wire interconnected by a coil-reversing loop, said coiled lengths being substantially coaxial with said path and including the same number of spaced coils of substantially the same coil pitch and diameter, said coiled lengths being in the form of an inverted helix of opposite hand. 

1. In a yarn-handling installation including spaced supports defining a path of advance for running yarn, a heater comprising two coiled lengths of electrical resistance wire interconnected by a coil-reversing loop, said coiled lengths being substantially coaxial with said path and including the same number of spaced coils of substantially the same coil pitch and diameter, said coiled lengths being in the form of a double stranded helix of the same hand.
 2. In a yarn-handling installation including spaced supports defining a path of advance for running yarn, a heater comprising two coiled lengths of electrical resistance wire interconnected by a coil-reversing loop, said coiled lengths being substantially coaxial with said path and including the same number of spaced coils of substantially the same coil pitch and diameter, said coiled lengths being in the form of an inverted helix of opposite hand. 